Device for reducing leakage in rotary engines at low running speeds

ABSTRACT

A device for reducing leakage between a rotor and a stator of a rotary engine at low running speeds is disclosed, the device comprising sealing elements at the end parts of the rotor teeth, adapted to come into frictional engagement with the internal surface of the stator at low speeds and to be disengaged in response to centrifugal forces, when the speed exceeds a predetermined value, the engine being then operated as a conventional engine of the gear type.

United States Patent Brille 51 Dec. 26, 1972 [54] DEVICE FOR REDUCING LEAKAGE IN ROTARY ENGINES AT LOW RUNNING SPEEDS [72] Inventor: Maurice Georges Brllle, Nanterre,

France [73] Assignee: Societe Anonyme de Vehiculee Industriels et d'Equipements Mecaniques, S.A.Y.I.E.M., Paris, France 221 Filed: 0ct.22,1970

21 App]. No.: 82,869

30 Foreign Application Priority um Oct. 23, 1969 France ..6936360 521 u.s.c|... ..41s/11s,41s/121 [51 Int.C1 ..F01c19/02,F03c3/00,F04c 27/00 [58] Field 0fSearch...'....418/i13,114,115,119-123 [56] References Cited UNITED STATES PATENTS 2,041,121 5/1936 Fareao ..418/115 3,444,843 5/1969 Sabet ..418/1 15 1,158,733 11/1915 Shepherd et a1 ..418/115 3,456,625 7/1969 Jones et a1 ..418/115 Primary Examiner-William L. Freeh Assistant Examiner-John J. Vrablik Attorney-Michael P. Breston 57 ABSTRACT A device for reducing leakage between a rotor and a stator of a rotary engine at low running speeds is disclosed, the device comprising sealing elements at the end parts of the rotor teeth, adapted to come into frictional engagement with the internal surface of the stator at low speeds and to be disengaged in response to centrifugal forces, when the speed exceeds a predetermined value, the engine beingthen operated as a conventional engine of the gear type.

7 Claims 2 Drawing Figures [I], III [III/1m DEVICE FOR REDUCING LEAKAGE IN ROTARY ENGINES AT LOW RUNNING SPEEDS BACKGROUND OF THE INVENTION This invention relates to a device for reducing leakage at the periphery of the rotors of rotary engines, particularly pumps or compressors of the gear type.

It is known that these engines have an acceptable yield only above a relatively high speed, due to the leakage at low speeds, resulting from the necessary clearance between rotors and stators. The leakage becomes negligible at the high output rates which correspond to high running speeds.

Accordingly, the use of such engines at low running speeds, where they are inefficient, has been avoided and when such working conditions were required it was preferred to make use of volumetric pumps or compressors of the piston or blade type which are more efficient at low running speeds, in spite of their higher specific power consumption, due to the friction of the piston rings or of the blades.

It is an object of this invention to avoid such a loss of energy by making the pumps or compressors of the gear type more efficient at low speeds, without substantial power loss.

SUMMARY OF THE INVENTION This object is achieved according to the invention by.

providing a device for reducing leakage at low speeds, the device comprising laterally and longitudinally extending sealing elements provided on the end parts of the teeth of the rotor, or rotors, of the pumps or compressors of the gear type, the sealing elements lying in an axial plane of the rotor. Thus, the sealing elements generate a family of axial contact lines with stator, usually the housing. The sealing elements bear with friction against the surfaces of the stator through resilient means, so that the sealing elements undergo, above a given rotational speed, a slight withdrawal preventing any contact and consequently any friction of the sealing elements with the corresponding internal surfaces of the stator, this withdrawal being performed through mechanical means actuated by centrifugal forces.

This arrangement makes it possible to make use of compressors and pumps of the gear type at low running speeds, since the frictional forces of the sealing members, or elements, against the longitudinal and lateral wall surfaces of the stator, which appear at low speeds, have the effect of reducing in a very largeproportion the leakage resulting from the necessary clearance between the stator and the rotor, or rotors, whereas the clearance is restored at high rotational speeds.

Above a certain running speed, at which the frictional forces developed by the sealing elements would result in an overheating and excessive power consumption, the withdrawal of the sealing elements, actuated by centrifugal forces, results in the discontinuance of such frictional contact and accordingly the engine operates as a conventional compressor or pump of the gear type, the increased output rate making negligible the proportion of the leakage due to the clearance.

Such a device is particularly efficient in compressors for supercharging Diesel engines, the rotational speed of which depends on the running speed of the engine, whereas a high compression of the air feed is essential at low speeds, particularly during idling and starting periods.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the device of the invention is described further below for illustrative purposes, the scope of the invention being by no way limited thereto, and with reference to the accompanying drawing, wherein:

FIG. 1 is a cross-sectional view along line I--I of FIG. 2 showing a gear compressor with two-teeth rotors equipped with the device according to the invention; and

FIG. 2 is a cross-sectional view of the same compressor along line 11- of FIG. 1, the upper and lower portions illustrating low and high speed conditions, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT It can be seen from the cross-sectional views of FIGS. 1 and 2 that the compressor comprises a housing 1, constituting the stator, wherein are rotatably mounted, on shafts 4 and 5, two gear rotors 2 and 3 provided with weight-reducing holes 6.

In a slot milled along an axial plane of each rotor tooth, alsoreferred to as a blade, due to the shape illustrated, are fitted, while freely sliding therein, a longitudinally extending sealing member, or element, 7 and two laterally extending sealing members, or elements, 8. The sealing element 7 is provided with two fastening lugs 9, and, of the sealing elements 8, each has a fastening lug 10. All lugs 9 and 10 terminate in a hooked portion engaging bearing pins 11 and 12 at one end of each of the levers 13, to form two short arms for each lever. Each lever is pivotable about its supporting shaft or pin 14, the pins 14 extending through the slots.

The other end constituting a relatively longer arm of each lever 13 bears against a small mass 15 placed in a central portion of the axial slot which extends to the bore containing the shaft 4 or 5.

Flat springs 16 and 17 provide the bearing, i.e. sealing, pressure of sealing elements 7 and 8 against the internal surface of the housing 1, which functions as the stator.

In operation, when the rotors are driven at low speed, the device is in the position shown in section in the upper half of FIG. 2, above axis A-A. In this case, the pressure developed by springs 16 and 17 urges the sealing elements 7 and 8 against the internal wall surface of the housing, thereby ensuring the sealing effect. The springs 16 and 17 apply, on the one hand, an axial pressure, in the direction of arrows F to sealing elements 8 and, on the other hand, a radial thrust, in the direction of arrows F to the sealing element 7, due to the anchoring of their ends into recesses 18 of sealing elements 8, to their S-shaped configuration, making possible their compression in two perpendicular directions and to the bearing of springs 16 on the bottom of the rotor slot.

In response to this pressure, the sealing elements 7 and 8 exert, through their connecting lugs 9 and I0 bearing on the short arms 11 and 12 of lever 13, a slight pressure on the other end of the lever, which is thus transmitted to the small mass 15 which remains accordingly urged against shaft 4 or 5.

,With an increasing rotational speed, the effect of centrifugal forces prevails over the force developed by springs 16 and 17, taking into account the amplification factordue to the lever system 13, even though small centrifugal forces are applied to sealing element 7.

The small mass then moves away from the shaft and causes the levers 13 to pivot. The long lever arms, which at this moment are thus rotated into a position substantially parallel to axis AA of the rotor, assume a position against the sealing elements as shown in cross section in the lower half of FIG. 2, below axis A- The rotation of levers 13 about pins 14 results, through the intermediary action of the short lever arms 11 and 12 and their entraining the hooks on the lugs 9 and 10, in the withdrawal of the sealing elements 7 and i 8 into the rotor slot, so that they are no longer in contact with the internal wall surface of the housing 1. The engine is thus operating as a conventional gear pump or compressor without frictional contact between the rotor or rotors and the stator, i.e. the housing. The frictional contact, with an attendant restoring of the sealing effect, is achieved as soon as the running speed becomes lower than a predetermined value.

Due to their simple shape, the sealing elements may be advantageously made of autolubricating fritted materials.

The effect which frictional forces have on the sensitivity of themechanism may be reduced by using relatively strong springs, balanced by small masses of relatively heavy alloys, e.g. lead alloys or lead.

Due to its simplicity of construction, the device of the invention may easily be built into the rotors of presently used engines which have initially not been designed therefor, and this can be done at a reasonable cost.

Thus, when each lever 13 has been mounted on its pin 14, the pins are welded or brazed at their ends to the surface of the rotor, the small mass 15 is introduced into the slot, with the levers l3 tilted back, i.e. the long arms oriented outwardly. The sealing element 7 is then placed into its proper location, with its lugs hooked onto the short arms 11 of lever 13. Then, sealing elements 8, provided with the springs 16 and 17, are driven into the slot until the hook-shaped ends of their fastening lugs 10 engage the short arms 12 of levers l3.

Disassembling the device is achieved by laterally sliding, causing disengagement, of sealing elements 7.-

The small width of the device, which is entirely enclosed in the slot accommodating the sealing elements, makes possible a substantial reduction in weight of the rotors by the provision of holes or recesses 6 therein.

What is claimed is:

l. A rotary engine having a stator and at least one rotor, lateral and longitudinal sealing'members at the end parts of the teeth of each rotor carried on fastening lugs and adapted to bear by frictional contact on the internal surface of the stator by the action of resilient means, a small mass, accommodated in an axially extending slot of the rotor, and displaceable in response to centrifugal forces to act against said resilient means so as to counterbalance the repelling force thereof at high running speeds of the engine, said engine comprising in combination:

at least two double-acting levers,

each lever being pivotably mounted on a pin across the slot, and each lever having a long arm displaceable by said smallmass and two short arms; one of said short arms bears against the fastening lug of a longitudinal sealing member and the other of said short arms bears against the fastening lug of a lateral sealing member so as to simultaneously control the withdrawal of said longitudinal and lateral sealing members in response to the displacement of said small mass, and

said short arms acting simultaneously against the oppositely-directed forces imparted to said fastening lugs by said resilient means.

2. A rotary engine according to claim 1 wherein the respective faces of said two short arms of each doubleacting lever are substantially perpendicular to each other and act respectively on the fastening lugs of the longitudinal and lateral sealing members.

3. A rotary engine according to claim 1 wherein,

said resilient means are S-shaped, flat springs which are simultaneously compressed along two perpendicular directions so as to exert a pressure on said longitudinal and lateral sealing members.

4. ln arotary engine of the character described and including at least one tooth-or blade-shaped rotor mounted for rotation within a stator, at least one sealing arrangement comprising:

sealing elements mounted on the rotor,

pressure means for applying sealing pressure to the sealing elements thereby to urge the sealing elements into surface contact with the stator,

reducing means for reducing the sealing pressure as a function of rotational speed of the rotor by controlling the withdrawal of the sealing members from contact with the stator, said reducing means including at least one mass mounted in each tooth,

or blade, of the rotor for displacement in a radial direction,

force-transmitting means accommodated within a slot in the rotor and operatively connected to said mass and said sealing elements and provided for withdrawing the sealing elements from surface contact with the stator when the centrifugal forces acting upon the mass increase with increasing rotational speed, one axially-extending sealing element and two radially-extending sealing elements, accommodated within and protruding from the slot,

said pressure means comprising resilient means for urging said sealing elements outwardly of the slot, and

said force-transmitting means including at least one lever having a driving arm displaced by the mass when moved radially outwardly by centrifugal forces, and two other arms which operate to withdraw the sealing elements away from the stator.

5. The combination of claim 4 wherein,

said sealing elements have inwardly-extending lugs terminating in hook-shaped end protions, and

each hook-shaped end portion engaging a distinct portion of one of said other arms of said lever to cause the withdrawal of said sealing elements.

6. The combination of claim 4 wherein,

the resilient means are flat springs which are doublecurved into a S-shaped configuration, thereby to simultaneously permit their resilient deformation in an axial and a radial direction.

7. The combination of claim 4 wherein,

said sealing elements are made of an auto-lubricating porous material. 

1. A rotary engine having a stator and at least one rotor, lateral and longitudinal sealing members at the end parts of the teeth of each rotor carried on fastening lugs and adapted to bear by frictional contact on the internal surface of the stator by the action of resilient means, a small mass, accommodated in an axially extending slot of the rotor, and displaceable in response to centrifugal forces to act against said resilient means so as to counterbalance the repelling force thereof at high running speeds of the engine, said engine comprising in combination: at least two double-acting levers, each lever being pivotably mounted on a pin across the slot, and each lever having a long arm displaceable by said small mass and two short arms; one of said short arms bears against the fastening lug of a longitudinal sealing member and the other of said short arms bears against the fastening lug of a lateral sealing member so as to simultaneously control the withdrawal of said longitudinal and lateral sealing members in response to the displacement of said small mass, and said short arms acting simultaneously against the oppositelydirected forces imparted to said fastening lugs by said resilient means.
 2. A rotary engine according to claim 1 wherein the respective faces of said two short arms of each double-acting lever are substantially perpendicular to each other and act respectively on the fastening lugs of the longitudinal and lateral sealing members.
 3. A rotary engine according to claim 1 wherein, said resilient means are S-shaped, flat springs which are simultaneously compressed along two perpendicular directions so as to exert a pressure on said longitudinal and lateral sealing members.
 4. In a rotary engine of the character described and including at least one tooth-or blade-shaped rotor mountEd for rotation within a stator, at least one sealing arrangement comprising: sealing elements mounted on the rotor, pressure means for applying sealing pressure to the sealing elements thereby to urge the sealing elements into surface contact with the stator, reducing means for reducing the sealing pressure as a function of rotational speed of the rotor by controlling the withdrawal of the sealing members from contact with the stator, said reducing means including at least one mass mounted in each tooth, or blade, of the rotor for displacement in a radial direction, force-transmitting means accommodated within a slot in the rotor and operatively connected to said mass and said sealing elements and provided for withdrawing the sealing elements from surface contact with the stator when the centrifugal forces acting upon the mass increase with increasing rotational speed, one axially-extending sealing element and two radially-extending sealing elements, accommodated within and protruding from the slot, said pressure means comprising resilient means for urging said sealing elements outwardly of the slot, and said force-transmitting means including at least one lever having a driving arm displaced by the mass when moved radially outwardly by centrifugal forces, and two other arms which operate to withdraw the sealing elements away from the stator.
 5. The combination of claim 4 wherein, said sealing elements have inwardly-extending lugs terminating in hook-shaped end protions, and each hook-shaped end portion engaging a distinct portion of one of said other arms of said lever to cause the withdrawal of said sealing elements.
 6. The combination of claim 4 wherein, the resilient means are flat springs which are double-curved into a S-shaped configuration, thereby to simultaneously permit their resilient deformation in an axial and a radial direction.
 7. The combination of claim 4 wherein, said sealing elements are made of an auto-lubricating porous material. 